Wire and textile reinforced high pressure elastomeric and thermoplastic hoses are well known for applications of hydraulic actuation and closed or open loop conveyance. Closed loop fluid conveyance refers to applications where the medium that passes through the hose is not released. One example of closed loop conveyance might be for heat transfer or dissipation or for cooling. Open loop conveyance refers to applications where a controlled amount of medium is released, for example, high pressure spray applications. As used herein the term “rubber” is synonymous with “elastomer” and refers to thermosetting, crosslinking, or curable materials, including natural and synthetic rubbers such as, but not limited to Neoprene®, nitrile, Buna N, styrenebutadiene rubber (SBR), Hypalon™, silicone and the like. Modern elastomeric materials are often devised of more than one rubber material and may contain other additives and/or be comprised of additional elements such as one or more thermoplastic constituent(s). The term “thermoplastic” means materials which are solid at room temperature and which soften at an elevated temperature repeatedly. Some examples, but by no means all that may apply to this invention, include thermoplastic materials such as nylon, polyester terephthalate, polyethylene, polyvinyl chloride, polyamide (nylon), ethylene vinyl acetate, polypropylene and polyurethane. Modern thermoplastic materials are often devised of more than one thermoplastic materials and may contain other additives and/or be comprised of additional elements such as one or more elastomeric or rubber constituent(s).
High pressure, thermoplastic yarn-reinforced hoses have been in existence for more than 50 years. In the early days of the product, there were no defined standards. Currently, the Society of Automotive Engineers (SAE) has adopted detailed standards that specify the base materials used in the stated hose types in order to meet the standards. The standards include materials, construction, dimensional tolerances and the dynamic test parameters for a wide range of hose types and sizes. Such details are amply described in the standards identified as SAE J343 and SAE J517.
Within these standards there are two main types of high pressure hoses described. One type is a rubber or elastomeric hose reinforced with braided or spiral layers of high tensile strength material, usually steel wire. Another type is a thermoplastic hose that is reinforced with textile yarn. For the purposes of the present invention, the specification pertaining to thermoplastic hose that is reinforced with textile yarn will be referenced. Specific and different types within that category are further defined within the standards SAE 100R7, 100R8 and 100R18.
The United States Patent of Brumbach, U.S. Pat. No. 3,062,241 discloses a plastic tube comprised of Nylon (Polyamide 11) plastic tubing over which is applied at least one layer of reinforcing fiber and an outer sheath of nylon. Said materials are very strong, but known to be problematic in the application as they are very stiff. Because of the stiffness of the nylon, this makes the final hose subject to flattening and kinking at a relatively small bend radius. In particular, this weakens the hose, and after repeated kinking the plastic becomes creased. Said creasing is defined as notch sensitivity to those familiar with the art, and said notch may eventually cause the inner tube or cover to rupture. Such a rupture will result in a potentially dangerous high pressure leak.
The United States Patent of Matthews, U.S. Pat. No. 3,116,760 discloses attempts to rectify the kinking issue by recommending the use of a highly flexible polyurethane inner tube and cover material and bonding the various layers with a heat and chemical process to form a lamination. These processes are expensive and dangerous as the use of high heat and solvent based adhesives are known to create toxicity and present a hazard to workers and the environment. Secondly, the concept requires that such process and machinery be duplicated on every reinforcing machine. This is not feasible, as one tube making line is able to support as many as about 20 yarn reinforcement machines. Lastly, while the embodiments described within Matthews certainly achieved a better kink resistance and higher degree of flexibility, no mention is made of the tendency for the hose to elongate when pressure equal to the specified working pressure is applied. For those familiar with the art, such elongation is known to occur with soft and highly flexible materials, even if fully or partially laminated.
Neither Brumbach nor Matthews teach about the change in length phenomena. SAE J517 and other standards reference a change in length maximum of plus or minus 3%. Change in length is often referred to as elongation. It simply means that when the hose is pressurized to the maximum specified working pressure, longitudinal forces can cause the hose to stretch or shrink. This shrinking or elongation can occur for a number of reasons, including elasticity of the inner tube material, braid reinforcement angle, yarn denier, yarn tensile strength, tension at which the yarn is applied, type of bonding and other reasons well known to those familiar with the art.
Hose braiding requires the intersecting of multiple strands of multifilament yarn which run in uniform opposite helical directions. To those familiar with the art, the ideal is a braid angle that is neutral. Such a neutral braid angle will result in a stable hose that will not change in length when pressurized. However, there are circumstances that can negatively influence the ideal. For example, when very soft materials are used, the longitudinal forces can cause the inner tube to stretch and the actual braid angle to narrow or reduce. For illustrative purposes, in an extreme example, the angle might change from 90° to 70°. Such change in angle results in a longer overall hose structure. It further redistributes and reduces the thickness of the yarn layer. Lastly, it moves the intersections of the yarn further apart longitudinally from each other. All three phenomena can dramatically reduce the burst pressure performance of the hose to below the desired minimum safety factor.
A further deleterious effect of elongation is that the hose stretches. If the hose is in a fixed position, it will move as it elongates. As the hose is pulsed by frequent changes in pressure, the result is a hose that is in constant movement. In the case of a tight installation, such movement can bring the cover into contact with surfaces that will abrade and damage the hose.
It is important to note that the terms “change in length and elongation” are not limited to only an increased length. Elongation can result in a positive increase in length or a negative change in length. In the case of a decrease in length, in a fixed application, the hose is shrinking. This can result in the hose pulling out of a connector or other fitting prematurely and without warning.
Additionally, it is well known to those familiar with the art, that the change in length of a particular hose is a very good indicator of impulse life. In the case of the SAE J517, the impulse test conditions are defined under which the hose must perform to at least 100,000 and as many as 300,000 impulses. For example a ¼″ ID hose produced to the SAE 100R18 standard, must withstand at least 200,000 impulses at nearly 4,000 PSI whereby the hose is pressurized and relaxed within various specified environmental controls. More preferably, hoses will perform to a higher level than the minimum defined in the standards for impulse. Most preferably, 1,000,000 impulses or more will be achieved. Change in length above 3% will dramatically reduce the life of the hose as the internal components are literally pulling against each other to separate, such separation will result in internal abrasion of the yarn, tube and material that will accelerate the hose failure at fewer than the standard impulse designation.
Change in length can be influenced and to some extent brought under control by several methods. One way can be by using tube or cover sheath materials that are very stiff. As in the case of Brumbach, the example of Polyamide (Nylon 11) is one example of such a material. However, the trade off is a finished hose structure that is also stiff, difficult to handle and prone to flattening, kinking and crimping. While such a concept could be acceptable in a fixed hydraulic application, for example on an agricultural tractor, a high degree of flexibility is desirous for an open loop spray type applications, two of which might be high pressure cleaning and airless paint spraying.
Matthews teaches that softer materials can be used, if the hose is somehow mechanically bonded to the inner tube and cover sheath. However, such bonding processes and materials have historically been very complex, expensive, toxic to workers and the environment and they achieve only limited results. As claimed by Matthews, the concept applies only to one nominal size of hose. The present invention would apply not only to more than one size of hose, but the principles can be applied to all nominal sizes as stated within the standards as well as additional fractional sizes as needed.
In fluid conveyance applications, hose storage reels or drums are frequently utilized where the hose is wound and stored on a reel or otherwise coiled against itself. In such applications, elongation of even 3% is not desirable. Such movement creates friction and thus heat and can result in eventual fusing or welding of one wound section to another, affecting a permanent joining of the parallel structures. This is particularly prone to occur when using preferred soft, tacky or elastic materials which contribute to the overall flexibility of the hose. This phenomenon can be addressed by using abrasion resistant additives or materials of a lower degree of elasticity. The prior solution is not economically acceptable and the latter solution stiffens the hose.
Other patents, for example United States Patent of Chudgar, U.S. Pat. No. 3,866,631, United States Patent of Koch U.S. Pat. No. 3,861,973 and United States Patent of Koch U.S. Pat. No. 3,914,146 and United States Patent of Chudgar, U.S. Pat. No. 3,944,453, build upon the idea of complex, expensive and often toxic methods resulting in lamination of nylon or polyester core tubes. None of these patents provide any teaching about elongation.
United States Patent of Ozawa, U.S. Pat. No. 5,380,571, does not teach bonding or lamination but does teach the incorporation of vulcanized rubber particles with thermoplastic and provides a well defined means of measuring flexural rigidity. However, the hose is produced by extruding over a mandrel, which adds at least three expensive steps to the normal thermoplastic hose production process. Further, there is no teaching about elongation in Ozawa.
United States Patent of Alexander, U.S. Pat. No. 5,964,409, teaches only one particular size of hose and claims elongation of no more than 3% at 25% of minimum burst pressure.
Therefore, an object of the invention is a high pressure thermoplastic hose that when kinked resists crimping and returns to its original shape.
A further object of the present invention is to produce a high strength high pressure textile reinforced thermoplastic hose that is very stable in length at up to 33% of the minimum designated burst pressure with or without chemical bonding between the layers.
A further object of the present invention is the method of using a highly economical, three stage process for variations of a braided hose that imparts all the benefits of high flexibility, small bend radii and length stability while being perfectly suitable for hydraulics, open or closed loop conveyance, and a electrically static dissipating hose suitable for conveyance of materials like solvent based paint and for use where outside environment is prone to explosion due to static electricity.
A further object is an economical method of producing a high strength highly flexible high pressure textile reinforced thermoplastic hose that is suitable for open or closed loop hydraulic applications.
Yet another object of the present invention is a method of manufacturing that stabilizes soft materials during the hose making process by using parallel strands of multifilament high tenacity yarn longitudinally and parallely applied during the reinforcement or braiding process.
A still further object of the present invention is a method of producing a very economical high strength highly flexible high pressure textile reinforced conductive and static dissipating high pressure hose suitable for spraying flammable materials or in flammable environments.